1. Field of the Invention
The present invention relates generally to waterboards and stiffening elements thereof.
2. Discussion of the Background
Sports boards composed of a preformed, preshaped, generally planar foam core with a slick bottom skin are very popular for use on water, snow, grass, ice or other surfaces. One type of sports board is a waterboard such as bodyboard or surf board and is employed in the water, more particularly for wave surfing. Generally, waterboards are made of semi-rigid foam core, typically with polystyrene foam, polyethylene foam or polypropylene foam, and have polyethylene foam sheets laminated to the top and side surfaces of the foam core, and have a bottom surface composed of a polymeric film material such as polyethylene or Surlyn® to provide a low-friction surface.
During wave riding, a user may bend the board and turn on the water. The board typically restores to a neutral position after bending. The recovery of the original shape is referred as the ‘memory’ of the foam core. Polypropylene foam cores have better memory characteristics than other foam core materials. Therefore, a polypropylene foam core is typically used for high end performance waterboards due to its resiliency, rigidity and light weight.
Typically, waterboards are ridden in a prone position, with one arm extending forward for gripping the nose of the board and the other arm positioned in a trailing manner for gripping the front portion of the side edge of the board. With the arms and hands thus positioned, the rider can push or pull against the engaged front or side edges to bend or twist the board to increase friction and drag on selected parts of the board, which helps the rider in redirecting the board. It is generally desirable to have a bodyboard with low flexibility (i.e., high stiffness) in the rearward portion of the board and higher flexibility in the forward portion of the board. This combination provides stiff support for the rider's body on the rearward portion of the board while allowing the rider to maneuver the board as described above.
A variety of stringers and stiffening methods have been described in the prior art. U.S. Pat. No. 6,036,560 (the '560 patent) discloses an encapsulated two-part stringer rod having a stiff portion in the body and tail of the bodyboard and a less stiff portion toward the nose of the bodyboard. The flexible front nose area provides greater maneuverability for the bodyboard. The '560 patent discloses an elongated stringer element comprising a stiff rear portion fabricated from fiberglass or graphite resin-impregnated material and a flexible front portion fabricated from a polyethylene material. the stringer is generally longitudinally arranged within the foam core material of the board and extends substantially from the tail end toward the front end.
U.S. Pat. No. 7,347,754 (the '754 patent) also discloses a two part encapsulated stringer providing greater stiffness in the body of the bodyboard and less stiffness in the nose of the bodyboard. The amount of stiffness imparted to the body is determined by a fiberglass tube and the amount of flexibility imparted to the nose is determined by a helical coil or spring.
The disadvantage of using an encapsulated stringer is that once a particular stiffness profile is selected at the time of manufacture, it cannot be changed. Riders vary in weight and strength and wave riding skills, so the optimum level of flexibility varies from rider to rider. It would be desirable, therefore, to provide a waterboard with externally adjustable stiffening element(s) configured to provide variable resistance to flex.